Array substrate of an organic light-emitting diode (OLED) display device includes a plurality of sub-pixels, in each of which an OLED for emitting light of corresponding color is provided, the OLED includes a cathode, an anode and a light-emitting layer. The light-emitting layer mainly includes an electroluminescent layer (for the purpose of emitting light of different colors), and may also include other layers such as an electron transport layer, an electron injection layer, a hole injection layer, a hole transport layer, etc. The light-emitting layer is generally formed by way of evaporation. For sub-pixels having different colors, because materials of the light-emitting layers thereof are different, the light-emitting layers thereof need to be formed separately by way of evaporation, that is, the light-emitting layers of the same color may be simultaneously formed by way of evaporation. In forming the light-emitting layer of each color by way of evaporation, it is necessary to use a Fine Metal Mask (FMM), which is a metal sheet (thickness thereof is typically 30-40 μm) with many openings, the openings correspond to positions where the light-emitting layers need to be formed, and thus evaporation material (material of the light-emitting layers) can only be evaporated and formed at the desired positions through the openings, without entering into sub-pixels of other colors.
With the development of technology, resolution of a display device is continuously improved, and therefore sizes of the sub-pixel and structures therein are continuously decreased. For a FMM, due to the limitation of technique and performance of material, size of the openings and distance between openings cannot be too small, which limit the smallest size of the light-emitting layer, thereby impacting improvement of resolution.